ScanCursor holds reference to closed/released Jedis connection [DATAREDIS-531]

[spring-projects-issues]

Mark Paluch opened DATAREDIS-531 and commented

The concurrent use of SCAN and iteration over the resulting Cursor causes various Exceptions using the Jedis Driver.

Test case: https://gist.github.com/mp911de/327cb876117bc1d74049aff25e5509cb

redis.clients.jedis.exceptions.JedisConnectionException: Unknown reply: 5
	at redis.clients.jedis.Protocol.process(Protocol.java:154)
	at redis.clients.jedis.Protocol.processMultiBulkReply(Protocol.java:196)
	at redis.clients.jedis.Protocol.process(Protocol.java:147)
	at redis.clients.jedis.Protocol.processMultiBulkReply(Protocol.java:196)
	at redis.clients.jedis.Protocol.process(Protocol.java:147)
	at redis.clients.jedis.Protocol.read(Protocol.java:205)
	at redis.clients.jedis.Connection.readProtocolWithCheckingBroken(Connection.java:297)
	at redis.clients.jedis.Connection.getRawObjectMultiBulkReply(Connection.java:242)
	at redis.clients.jedis.Connection.getObjectMultiBulkReply(Connection.java:248)
	at redis.clients.jedis.BinaryJedis.hscan(BinaryJedis.java:3300)
	at org.springframework.data.redis.connection.jedis.JedisConnection$5.doScan(JedisConnection.java:3437)

java.lang.ClassCastException: [B cannot be cast to java.util.List
	at redis.clients.jedis.Connection.getRawObjectMultiBulkReply(Connection.java:242)
	at redis.clients.jedis.Connection.getObjectMultiBulkReply(Connection.java:248)
	at redis.clients.jedis.BinaryJedis.hscan(BinaryJedis.java:3300)
	at org.springframework.data.redis.connection.jedis.JedisConnection$5.doScan(JedisConnection.java:3437)

This issue gets only visible if:

1. Multiple threads try to use the SCAN command and iterate over the resulting Cursor
2. There is enough data to keep the iteration busy

The reason is that the resulting Cursor s hold a reference to the connection that was allocated during the .scan() invocation. .scan() allocates a connection but then it releases the connection back and so can multiple Cursors in different Thread s share the same Jedis connection

---

Affects: 1.7.2 (Hopper SR2)

Reference URL: redis/jedis#918

Attachments:

• SpringDataRedisTests.java (3.02 kB)

Issue Links:

• DATAREDIS-550 ScanCursor holds reference to closed/released lettuce connection

• DATAREDIS-454 SSCAN: Connection Used After Being Released
  ("supersedes")

• DATAREDIS-382 Using SCAN commands causes issues with Jedis in multi-threaded use
  ("supersedes")

Referenced from: pull request #218